1. Field of the Invention
The present invention relates to systems and methods for providing video program material to subscribers, and in particular to a method and system for minimizing conditional access information while ensuring reception of conditional access information in multi-tuner receivers.
2. Description of the Related Art
Media programs such as video and audio information can be distributed to households via a variety of methods including terrestrial transmitters, cable, the Internet, and satellites. Each of these media distribution systems implement a large number of channels, and are therefore capable of providing a large number of concurrently broadcast media programs to each household.
While existing systems provide a large number of channels, there is a trend towards even greater numbers of channels and greater bandwidth requirements on existing channels to accommodate, for example, HDTV. With regard to satellite-based media program distribution systems, the increased channels and bandwidth demands can be satisfied by the introduction of additional satellites and/or the use of additional transponders on the satellites.
In order to receive signals from each of the plurality of satellites, ground stations can include multiple antennae (each directed to a satellite of interest) coupled to a single tuner, multiple receiving elements (referred to as low noise block converters, or LNBs) using a single reflector, or multiple antennae and multiple tuners.
At the same time, it is important that the media programs transmitted by the satellites be protected from unauthorized reception and/or reproduction. This is accomplished by encrypting the media programs, and broadcasting data that (along with hardware disposed at the receiver station) is used to decrypt the media programs.
Conditional access information is sent to the subscriber's receivers to authorize presentation of the media programs. Control access information is also used to cancel service, renew service, and to transmit other information to the subscriber's receiver. This information is usually transmitted in data packets called control access packets (CAPs). The user's receiver routes the packets to a control access module (CAM). Using the control access information, the CAM allows the encrypted media programs to be decrypted, this activating/deactivating service. Generally, CAPs are transmitted to all subscribers on all channels.
Subscriber receivers include single tuner and multiple tuner models. In both single-tuner and multiple tuner models, the tuner receives the CAPs that are transmitted by the transponder to which the tuner is tuned. In single-tuner models, all CAPs received by the tuner are simply sent to the CAM. However, in multiple tuner models, sending all CAPs received from all tuners to the CAM results in wasteful data redundancy on the tuner-CAM transport path, since many of the CAPs coming from different tuners will be the same.
Tuner-CAM data redundancy can be reduced by only sending CAPs from one of the tuners to the conditional access module. However, this solution could result in the loss of some CAPs, specifically, those CAPs that are sent only on selected transponders. One solution would be to transmit all CAPs on all transponders. However, this would increase data redundancy in the broadcast channels. What is needed is a system and method for efficiently providing CAPs to single-tuner and multi-tuner receivers for use in decrypting media programs. The present invention satisfies that need.